The Norks have been indoctrinated for decades. It doesn't surprise me that they could get that many volunteers or many more. They're taught from preschool age that Americans rape Korean women and eat children as well as every other conceivable atrocity.
3.5 million volunteers added to their active duty and reservist and paramilitary personnel (about 7.5 million in all, per 2016 Wikipedia article), brings their total under arms to 11 million. This is about
44 percent of their entire population including women and children and elderly. If we assume a fourth of their population, say, 9 million people, are not suited for military or at least paramilitary service, then the 11 million people uinder arms amount to almost
60 percent of all their able-bodied people. That percentage tends to confirm that the Norks are a monstrously fanatical people as a whole. The really spooky thing about that is that it suggests that we may not need to worry as much as we normally do about civilian casualties. It looks like practically their whole country is our bitter enemy (just as you suggested).
I really do feel sorry for them. But ignorant or not, they should have taken out the Fat Boy long before now.